HES1 and glioblastoma: Subsequently, we determined whether blocking of the Notch pathway could overcome the EFEMP1-mediated resistance to TMZ, by treating the Hs683-WT and Hs683-Rl glioblastoma cells that demonstrated high expression of HES1/HEY1 with TMZ and the γ-secretase inhibitor (GSI) DAPT (Fig. 3C).